Tissue injuries such as mucosal injury, vascular injury and the like occur when general medical devices composed of plastics, metals, ceramics and the like are inserted into the living body and contacted strongly with biological tissues. In concrete terms, when a catheter, a guide wire, an endoscope, a rectal thermometer probe or the like is inserted into a blood vessel, a digestive organ or the like hollow organ until it reaches the intended position, various tissue injuries including mucosal injury and vascular injury occur which give patients pain and cause prolongation of therapeutic period. Also, in some cases, a medical device cannot be inserted into the intended position due to its large insertion resistance. In consequence, in order to lessen these injuries or reduce the insertion resistance, various measures have been taken in the prior art for example by using a low friction material as the base material, coating the device surface with oils which give lubricity or with a hydrophilic polymer or fixing a hydrophilic polymer to the surface making use of covalent bond, ionic bond and the like chemical bonds.
Illustrative examples of the low friction material include polyethylene, polyacetal, fluorocarbon resin and the like, and those of the lubricity-providing oil include silicone oil, olive oil, glycerol and the like. With regard to the method for fixing a hydrophilic polymer to the material surface, JP-B-59-19582 discloses a method in which polyvinyl pyrrolidone or the like is fixed making use of isocyanate group (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-59-81341 discloses a method in which two or more hydrophilic polymers are fixed also making use of isocyanate group (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-58-193766 discloses a method in which polyethylene oxide is fixed also making use of isocyanate group. However, such low friction materials are not effective in sufficiently preventing tissue injuries, and continual presence of lubricity cannot be obtained by the method in which oils or hydrophilic polymers are used. Also, since a substance having high reactivity (isocyanate group or the like) is used in the fixation of a hydrophilic polymer to the surface, it is probable that the substance when remained will cause a problem due to its toxicity. In addition, when the method in which an oil or a hydrophilic polymer is used is employed in the production process of medical devices, the process becomes complex due, for example, to the increased number of operation steps.
Thus, as has been described in the foregoing, the prior art methods for adding lubricity to the surface of a medical device have disadvantages in that production process of the device becomes complex, its lubricity cannot be maintained continually and when chemicals having high reactivity are used, its safety cannot be maintained depending on a situation.